International Mobile Equipment Identity
Encyclopedia
The International Mobile Equipment Identity or IMEI (icon) is a number, usually unique, to identify GSM, WCDMA, and iDEN
mobile phone
s, as well as some satellite phone
s. It is usually found printed inside the battery compartment of the phone. It can also be displayed on the screen of the phone by entering*#06# into the keypad on most phones.
The IMEI number is used by the GSM network to identify valid devices and therefore can be used for stopping a stolen phone from accessing the network in that country. For example, if a mobile phone
is stolen, the owner can call his or her network provider and instruct them to "blacklist" the phone using its IMEI number. This renders the phone useless on that network and sometimes other networks too, whether or not the phone's SIM
is changed.
The IMEI is only used for identifying the device and has no permanent or semi-permanent relation to the subscriber. Instead, the subscriber is identified by transmission of an IMSI number, which is stored on a SIM card that can (in theory) be transferred to any handset. However, many network and security features are enabled by knowing the current device being used by a subscriber.
, under the Mobile Telephones (Re-programming) Act, changing the IMEI of a phone, or possessing equipment that can change it, is considered an offence under some circumstance. Such an action is also considered a criminal offence in Latvia
.
IMEI blocking is not the only approach available for combating phone theft. For example, mobile operators in Singapore are not required by the regulator to implement phone blocking or tracing systems, IMEI-based or other. The regulator has expressed its doubts on the real effectiveness of this kind of system in the context of the mobile market in Singapore. Instead, mobile operators are encouraged to take measures such as the immediate suspension of service and the replacement of SIM cards in case of loss or theft.
There is a misunderstanding amongst some regulators that the existence of a formally-allocated IMEI number range for a GSM terminal implies that the terminal is approved or complies with regulatory requirements. This is not the case. The linkage between regulatory approval and IMEI allocation was removed in April 2000, with the introduction of the European R&TTE Directive. Since that date, IMEIs have been allocated by BABT
(or one of several other regional administrators acting on behalf of the GSM Association
) to legitimate GSM terminal manufacturers without the need to provide evidence of approval.
(CEIR) which blacklists the device in all other operator switches that use the CEIR. With this blacklisting in place the device becomes unusable on any operator that uses the CEIR, making theft of mobile equipment a useless business proposition, unless for parts.
The IMEI number is not supposed to be easy to change, making the CEIR blacklisting effective. However this is not always the case: a phone's IMEI may be easy to change with special tools.
(TAC). The remainder of the IMEI is manufacturer-defined, with a Luhn check digit
at the end. For the IMEI format prior to 2003,
the GSMA guideline was to have this Check Digit always transmitted to the network as zero. This guideline seems to have disappeared for the format valid from 2003 and onwards.
, the format of the IMEI is AA-BBBBBB-CCCCCC-D, although it may not always be displayed this way. The IMEISV drops the Luhn check digit in favour of an additional two digits for the Software Version Number (SVN), making the format AA-BBBBBB-CCCCCC-EE
Prior to 2002, the TAC was six digits long and was followed by a two-digit Final Assembly Code (FAC), which was a manufacturer-specific code indicating the location of the device's construction.
From January 1, 2003 until that April 1, 2004, the FAC for all phones was 00.
After April 1, 2004, the Final Assembly Code ceased to exist and the Type Allocation Code increased to eight digits in length.
In any of the above cases, the first two digits of the TAC are the Reporting Body Identifier
, which identifies the GSMA-approved group that allocated the TAC. The RBI numbers are allocated by the Global Decimal Administrator. The first two digits are always decimal (i.e., less than 0xA0), allowing IMEI numbers to be distinguished from an MEID
, which will always have 0xA0 or larger as its first two digits.
For example, the old style IMEI code 35-209900-176148-1 or IMEISV code 35-209900-176148-23 tells us the following:
By contrast, the new style IMEI code 49-015420-323751 has a 8-digit TAC of 49-015420.
The new CDMA Mobile Equipment Identifier (MEID
) uses the same basic format as the IMEI.
calculated using the Luhn algorithm
.
According to the IMEI Allocation and Approval Guidelines,
The check digit is validated in three steps:
Conversely, one can calculate the IMEI by choosing the check digit that would give a sum divisible by 10. For the example IMEI 49015420323751?,
To make the sum divisible by 10, we set ? = 8, so the IMEI is 490154203237518.
, Iridium and Thuraya
satellite phone
networks all use IMEI numbers on their transceiver units as well as SIM cards in much the same way as GSM phones do. The Iridium 9601 modem relies solely on its IMEI number for identification and uses no SIM card; however, Iridium is a proprietary network and the device is incompatible with regular GSM networks.
The IMEI number of a GSM device can be retrieved by sending the command AT+CGSN.
For more information, refer to the 3GPP TS 27.007, Section 5.4 /2/ standards document.
Retrieving IMEI Information from an older Sony
or Sony Ericsson
handset can be done by entering these keys: * Right * Left Left * Left *
IMEI information on BlackBerry
and on new Sony Ericsson devices can also be found by going to options, then status. On Android the IMEI information can be found under the "About Phone" menu option in the settings menu. On iOS
devices, the IMEI can be found under General: About in the Settings app.
Iden
For other uses of the word, see Iden The Iden was an English automobile manufactured from 1904 until 1907. Designed by George Iden, formerly of Daimler, they were four-cylinder 10/17 hp and 25/35 hp shaft-driven cars; each came with "Idens's frictionless radial gearbox"....
mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s, as well as some satellite phone
Satellite phone
A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites...
s. It is usually found printed inside the battery compartment of the phone. It can also be displayed on the screen of the phone by entering
The IMEI number is used by the GSM network to identify valid devices and therefore can be used for stopping a stolen phone from accessing the network in that country. For example, if a mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
is stolen, the owner can call his or her network provider and instruct them to "blacklist" the phone using its IMEI number. This renders the phone useless on that network and sometimes other networks too, whether or not the phone's SIM
Subscriber Identity Module
A subscriber identity module or subscriber identification module is an integrated circuit that securely stores the International Mobile Subscriber Identity and the related key used to identify and authenticate subscriber on mobile telephony devices .A SIM is held on a removable SIM card, which...
is changed.
The IMEI is only used for identifying the device and has no permanent or semi-permanent relation to the subscriber. Instead, the subscriber is identified by transmission of an IMSI number, which is stored on a SIM card that can (in theory) be transferred to any handset. However, many network and security features are enabled by knowing the current device being used by a subscriber.
IMEI and the law
Many countries have acknowledged the use of the IMEI in reducing the effect of mobile phone theft. For example, in the United KingdomUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, under the Mobile Telephones (Re-programming) Act, changing the IMEI of a phone, or possessing equipment that can change it, is considered an offence under some circumstance. Such an action is also considered a criminal offence in Latvia
Latvia
Latvia , officially the Republic of Latvia , is a country in the Baltic region of Northern Europe. It is bordered to the north by Estonia , to the south by Lithuania , to the east by the Russian Federation , to the southeast by Belarus and shares maritime borders to the west with Sweden...
.
IMEI blocking is not the only approach available for combating phone theft. For example, mobile operators in Singapore are not required by the regulator to implement phone blocking or tracing systems, IMEI-based or other. The regulator has expressed its doubts on the real effectiveness of this kind of system in the context of the mobile market in Singapore. Instead, mobile operators are encouraged to take measures such as the immediate suspension of service and the replacement of SIM cards in case of loss or theft.
There is a misunderstanding amongst some regulators that the existence of a formally-allocated IMEI number range for a GSM terminal implies that the terminal is approved or complies with regulatory requirements. This is not the case. The linkage between regulatory approval and IMEI allocation was removed in April 2000, with the introduction of the European R&TTE Directive. Since that date, IMEIs have been allocated by BABT
British Approvals Board for Telecommunications
The British Approvals Board for Telecommunications is the world's leading Telecommunications Certification Body.-State monopoly:It was established in July 1982 by the UK government to provide type approval services to the telecommunications terminal industry...
(or one of several other regional administrators acting on behalf of the GSM Association
GSM Association
The GSM Association is an association of mobile operators and related companies devoted to supporting the standardizing, deployment and promotion of the GSM mobile telephone system...
) to legitimate GSM terminal manufacturers without the need to provide evidence of approval.
Blacklist of stolen devices
When mobile equipment is stolen or lost the owner can typically contact their local operator with a request that it should be blocked. If the local operator possesses an Equipment Identity Register (EIR), it then will put the device IMEI into it, and can optionally communicate this to the Central Equipment Identity RegisterCentral Equipment Identity Register
The Central Equipment Identity Register is a database of the IMEI numbers of blacklisted handsets. If a device's IMEI number is listed on CEIR, it is not supposed to work on any service provider.A common usage of the CEIR is with stolen cellphones...
(CEIR) which blacklists the device in all other operator switches that use the CEIR. With this blacklisting in place the device becomes unusable on any operator that uses the CEIR, making theft of mobile equipment a useless business proposition, unless for parts.
The IMEI number is not supposed to be easy to change, making the CEIR blacklisting effective. However this is not always the case: a phone's IMEI may be easy to change with special tools.
Limitations
- "New IMEIs can be programmed into stolen handsets and 10% of IMEIs are not unique." According to a BT Cellnet spokesman quoted by the BBC.
- IMEIs can sometimes be unlisted depending on local arrangements. This would typically include quoting a password which was chosen at the time the blacklisting was applied.
Lawful interception
A target for lawful interception (wiretapping) can be specified by its IMEI number as well as IMSI and MSISDNStructure of the IMEI and IMEISV (IMEI Software Version)
The IMEI (14 decimal digits plus a check digit) or IMEISV (16 digits) includes information on the origin, model, and serial number of the device. The structure of the IMEI/SV are specified in 3GPP TS 23.003. The model and origin comprise the initial 8-digit portion of the IMEI/SV, known as the Type Allocation CodeType Allocation Code
The Type Allocation Code is the initial eight-digit portion of the 15-digit IMEI code used to uniquely identify wireless devices.The Type Allocation Code identifies a particular model of wireless telephone for use on a GSM, UMTS or other IMEI-supporting wireless network.The first two digits of...
(TAC). The remainder of the IMEI is manufacturer-defined, with a Luhn check digit
Luhn algorithm
The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm,is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in US and Canadian Social Insurance Numbers...
at the end. For the IMEI format prior to 2003,
the GSMA guideline was to have this Check Digit always transmitted to the network as zero. This guideline seems to have disappeared for the format valid from 2003 and onwards.
, the format of the IMEI is AA-BBBBBB-CCCCCC-D, although it may not always be displayed this way. The IMEISV drops the Luhn check digit in favour of an additional two digits for the Software Version Number (SVN), making the format AA-BBBBBB-CCCCCC-EE
| AA | - | BB | BB | BB | - | CC | CC | CC | D or EE | |
|---|---|---|---|---|---|---|---|---|---|---|
| Old IMEI | TAC | FAC | Serial number | (Optional) Luhn checksum Luhn algorithm The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm,is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in US and Canadian Social Insurance Numbers... |
||||||
| New IMEI | TAC | |||||||||
| Old IMEISV | TAC | FAC | Software Version Number (SVN). | |||||||
| New IMEISV | TAC | |||||||||
Prior to 2002, the TAC was six digits long and was followed by a two-digit Final Assembly Code (FAC), which was a manufacturer-specific code indicating the location of the device's construction.
From January 1, 2003 until that April 1, 2004, the FAC for all phones was 00.
After April 1, 2004, the Final Assembly Code ceased to exist and the Type Allocation Code increased to eight digits in length.
In any of the above cases, the first two digits of the TAC are the Reporting Body Identifier
Reporting Body Identifier
The Reporting Body Identifier is the first two digits of a GSM Type Allocation Code, and indicates the GSMA-approved organization that registered a given mobile device, and allocated the model a unique code....
, which identifies the GSMA-approved group that allocated the TAC. The RBI numbers are allocated by the Global Decimal Administrator. The first two digits are always decimal (i.e., less than 0xA0), allowing IMEI numbers to be distinguished from an MEID
MEID
A mobile equipment identifier is a globally unique number identifying a physical piece of CDMA mobile station equipment. The number format is defined by the but in practical terms it can be seen as an IMEI but with hexadecimal digits....
, which will always have 0xA0 or larger as its first two digits.
For example, the old style IMEI code 35-209900-176148-1 or IMEISV code 35-209900-176148-23 tells us the following:
TAC: 35-2099 - issued by the BABT (code 35) with the allocation number 2099
FAC: 00 - indicating the phone was made during the transition period when FACs were being removed.
SNR: 176148 - uniquely identifying a unit of this model
CD: 1 so it is a GSM Phase 2 or higher
SVN: 23 - The "software version number" identifying the revision of the software installed on the phone. 99 is reserved.
By contrast, the new style IMEI code 49-015420-323751 has a 8-digit TAC of 49-015420.
The new CDMA Mobile Equipment Identifier (MEID
MEID
A mobile equipment identifier is a globally unique number identifying a physical piece of CDMA mobile station equipment. The number format is defined by the but in practical terms it can be seen as an IMEI but with hexadecimal digits....
) uses the same basic format as the IMEI.
Check digit computation
The last number of the IMEI is a check digitCheck digit
A check digit is a form of redundancy check used for error detection, the decimal equivalent of a binary checksum. It consists of a single digit computed from the other digits in the message....
calculated using the Luhn algorithm
Luhn algorithm
The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm,is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in US and Canadian Social Insurance Numbers...
.
According to the IMEI Allocation and Approval Guidelines,
The Check Digit shall be calculated according to Luhn formula (ISO/IEC 7812). (See GSM 02.16 / 3GPP 22.016). The Check Digit is a function of all other digits in the IMEI. The Software Version Number (SVN) of a mobile is not included in the calculation.
The purpose of the Check Digit is to help guard against the possibility of incorrect entries to the CEIR and EIR equipment.
The presentation of the Check Digit both electronically and in printed form on the label and packaging is very important. Logistics (using bar-code reader) and EIR/CEIR administration cannot use the Check Digit unless it is printed outside of the packaging, and on the ME IMEI/Type Accreditation label.
The check digit is not transmitted over the radio interface, nor is it stored in the EIR database at any point. Therefore, all references to the last three or six digits of an IMEI refer to the actual IMEI number, to which the check digit does not belong.
The check digit is validated in three steps:
- Starting from the right, double a digit every two digits (e.g., 7 → 14).
- Sum the digits (e.g., 14 → 1 + 4).
- Check if the sum is divisible by 10.
Conversely, one can calculate the IMEI by choosing the check digit that would give a sum divisible by 10. For the example IMEI 49015420323751?,
| IMEI | 4 | 9 | 0 | 1 | 5 | 4 | 2 | 0 | 3 | 2 | 3 | 7 | 5 | 1 | ? |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Double every other | 4 | 18 | 0 | 2 | 5 | 8 | 2 | 0 | 3 | 4 | 3 | 14 | 5 | 2 | ? |
| Sum digits | 4 + (1 + 8) + 0 + 2 + 5 + 8 + 2 + 0 + 3 + 4 + 3 + (1 + 4) + 5 + 2 + ? = 52 + ? | ||||||||||||||
To make the sum divisible by 10, we set ? = 8, so the IMEI is 490154203237518.
Usage on satellite phone networks
The BGANBGAN
The Broadband Global Area Network is a global Satellite Internet Network with telephony using portable terminals. The terminals are normally used to connect a laptop computer to broadband Internet in remote locations, although as long as line-of-sight to the satellite exists, the terminal can be...
, Iridium and Thuraya
Thuraya
Thuraya , the Arabic name of the Pleiades, is a regional satellite phone provider. Its coverage area is most of Europe, the Middle East, North, Central and East Africa, Asia and Australia....
satellite phone
Satellite phone
A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites...
networks all use IMEI numbers on their transceiver units as well as SIM cards in much the same way as GSM phones do. The Iridium 9601 modem relies solely on its IMEI number for identification and uses no SIM card; however, Iridium is a proprietary network and the device is incompatible with regular GSM networks.
Retrieving IMEI information from a GSM device
On many devices, the IMEI number can be retrieved by entering *#06#, or using the AT command ATD*#06#.The IMEI number of a GSM device can be retrieved by sending the command AT+CGSN.
For more information, refer to the 3GPP TS 27.007, Section 5.4 /2/ standards document.
Retrieving IMEI Information from an older Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
or Sony Ericsson
Sony Ericsson
Sony Ericsson Mobile Communications AB is a joint venture established on October 1, 2001 by the Japanese consumer electronics company Sony Corporation and the Swedish telecommunications company Ericsson to manufacture mobile phones....
handset can be done by entering these keys: * Right * Left Left * Left *
IMEI information on BlackBerry
BlackBerry
BlackBerry is a line of mobile email and smartphone devices developed and designed by Canadian company Research In Motion since 1999.BlackBerry devices are smartphones, designed to function as personal digital assistants, portable media players, internet browsers, gaming devices, and much more...
and on new Sony Ericsson devices can also be found by going to options, then status. On Android the IMEI information can be found under the "About Phone" menu option in the settings menu. On iOS
IOS
iOS is an operating system for iPad, iPhone, iPod Touch, and Apple TV.IOS may also refer to:-Companies and organisations:* Illinois Ornithological Society, American state-based bird club...
devices, the IMEI can be found under General: About in the Settings app.
See also
- International Mobile Subscriber IdentityInternational Mobile Subscriber IdentityAn International Mobile Subscriber Identity or IMSI is a unique identification associated with all GSM and UMTS network mobile phone users. It is stored as a 64 bit field in the SIM inside the phone and is sent by the phone to the network...
- Luhn algorithmLuhn algorithmThe Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm,is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in US and Canadian Social Insurance Numbers...
- MEID
- Mobile phoneMobile phoneA mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
- UnlockingSIM lockA SIM lock, simlock, network lock or subsidy lock is a capability built into GSM phones by mobile phone manufacturers. Network providers use this capability to restrict the use of these phones to specific countries and network providers...
External links
- IMEI Allocation & Approval Guidelines: PDF document explaining IMEI in detail from GSM AssociationGSM AssociationThe GSM Association is an association of mobile operators and related companies devoted to supporting the standardizing, deployment and promotion of the GSM mobile telephone system...
.